Sterilizer casing for a telephone handset



FIG. 1 is a front and right side perspective view of a sterilizer casing for a telephone handset showing my new design;

FIG. 2 is a side elevational view thereof, the side opposite being a mirror image; and

FIG. 3 is a bottom plan view thereof. 

The ornamental design for a sterilizer casing for a telephone handset, as shown and described. 